From: The Coldest Winter: America and the Korean War, by David Halberstam (Hyperion, 2007), p. 13:

For experienced officers making the trek as the temperature dropped alarmingly, and the terrain became more mountainous and forbidding, there was an eerie quality to the advance. Years later, General Paik Sun Yup, commander of the South Korean First Division (and considered by the Americans the best of the Korean commanders), remembered his own uneasiness as they moved forward without resistance. There was a sense of almost total isolation, as if they were too alone. At first, Paik, a veteran officer who had once fought with the Japanese Army, could not pinpoint what bothered him. Then it struck him: the absolute absence of people, the overwhelming silence that surrounded his troops. In the past, there had always been lots of refugees streaming south. Now the road was empty, as if something important were taking place, just beyond his view and his knowledge. Besides, it was getting colder all the time. Every day the temperature seemed to drop another few degrees.

Certain key intelligence officers were nervous as well. They kept getting small bits of information, from a variety of sources, that made them believe that the Chinese had already entered North Korean territory by late October—and in strength. Colonel Percy Thompson, G-2 (or intelligence officer) for First Corps, under which the [U.S. First] Cav operated, and considered one of the ablest intelligence officers in Korea, was very pessimistic. He was quite sure of the Chinese presence, and he tried to warn his superiors. Unfortunately he found himself fighting a sense of euphoria that had permeated some of the upper ranks of the Cav and originated in Tokyo. Thompson had directly warned Colonel Hal Edson, commander of the Eighth Regiment of the First Cavalry Division, that he believed there was a formidable Chinese presence in the area, but Edson and others treated his warnings, he later noted, “with disbelief and indifference.” In the days that followed, his daughter Barbara Thompson Eisenhower (married to Dwight Eisenhower’s son John) remembered a dramatic change in the tone of her father’s letters from Korea. It was as if he were writing to say farewell. “He was absolutely sure they were going to be overrun, and he was going to be killed.” she later remembered.

Thompson had good reason to be uneasy. His early intelligence reads were quite accurate: the Chinese were already in country, waiting patiently in the mountains of Northern Korea for the ROKs and perhaps other UN units to extend their already strained logistical lines ever farther north. They had not intended to hit an American unit that early in the campaign. They wanted the Americans to be even farther north when they struck; and they knew the difficulty of the march north made their own job easier.

I distinctly remember seeing the First Cavalry shoulder insignia during my second grade year in elementary school at Camp Botanical Garden army base in Kyoto, Japan, in 1956-57, the last year before the base closed, the site reverted to its prior function, and the foreign missionaries had to start their own school.